x86: CONFIG_CC_STACKPROTECTOR=y is no longer experimental

This feature has been around for over 5 years now, and has no
CONFIG_EXPERIMENTAL dependency anymore, so remove the '(EXPERIMENTAL)'
tag from the help text as well.

Signed-off-by: Jean Delvare <jdelvare@suse.de>
Acked-by: Arjan van de Ven <arjan@linux.intel.com>
Link: http://lkml.kernel.org/r/1341583705.4655.18.camel@amber.site


Signed-off-by: Ingo Molnar <mingo@kernel.org>